Many methods are used to inject medicaments into a target site. These include syringes, auto-injectors, and drug pumps. The medicament can be injected at a variety of depths. For example, the medicament can be injected into the epidermis, the dermis, the subcutaneous region, or into the muscles (intramuscular). Some of these devices are specifically intended for at home use by a patient. These devices can be used to deliver a variety of medicaments. For example, the injectors can be used for the delivery of epinephrine to patients who are at risk of anaphylaxis. Such devices include the ANAPEN™ injector sold by Lincoln Medical Ltd. of the United Kingdom and the EPIPEN® injector sold by Mylan Inc. of Pennsylvania.
Many injectors use powerful springs to drive a plunger rod into a pre-filled syringe and inject the medicament into the tissue while pushing the injector into the side of the leg or other body location. Some of these injectors have the advantage of shielding the needle before and/or after use, thereby benefiting patients who have a fear of needles. Present injectors can contain more than twenty-six parts and be complicated to assemble due to the amount and complexity of the parts, which results in high prices to the user. The additional parts also increase the chance of failure of these complex devices.